Composição química e digestibilidade ruminal in situ da forragem de quatro espécies do gênero Brachiaria / Chemical composition and in situ ruminal degradability of four Brachiaria species

Avaliaram-se a composição química e a cinética da digestibilidade ruminal in situ da matéria seca (MS), proteína bruta (PB) e fibra em detergente neutro (FDN) da forragem de quatro espécies de Brachiaria, com 56 dias de crescimento, coletadas por corte manual. Foram utilizadas três vacas mestiças Holandês x Zebu, fistuladas no rúmen. Foram observados teores de 21,0; 21,1; 20,5 e 19,6 por cento de MS; 7,5; 6,4; 6,8 e 7,0 por cento de PB; e 66,8; 70,1; 73,4 e 63,9 por cento de FDN, respectivamente, para B. brizantha, B. decumbens, B. humidicola e B. ruziziensis. O maior valor nutricional foi da B. ruziziensis, que apresentou as mais elevadas taxas de degradação e degradabilidades efetivas (DE) da MS e da PB, e o menor teor de FDN associado à maior taxa de degradação desse nutriente. A forragem de pior qualidade nutricional foi B. humidicola, com menores valores de DE da MS e PB e maiores concentrações das frações fibrosas e indigestíveis.

The chemical composition and the ruminal in situ degradability of dry matter (DM), crude protein (CP), and neutral detergent fiber (NDF) of four species of Brachiaria were evaluated. The forages were harvested at 56 days of growth. Three rumen-fistulated crossbred Holstein × Zebu cows were used. The chemical composition of B. brizantha, B. decumbens, B. ruziziensis, and B. humidicola forages were, respectively: 21.0, 21.1, 20.5, and 19.6 percent for DM; 7.5, 6.4, 6.8, and 7.0 percent for CP; and 66.8, 70.1, 73.4, and 63.9 percent for NDF. B. ruziziensis presented the best nutritional value among the Brachiaria species, as indicated by the highest effective degradability (ED) and ruminal degradation rates of both DM and CP. B. ruziziensis also showed the highest NDF ruminal degradation rate and the lowest NDF concentration. In contrast, B. humidicola showed the worst nutritional composition, as indicated by the lowest DM and CP ED values and the highest content of indigestible and fibrous fractions.

Pollen mother cells of Tradescantia clone 4430 and Tradescantia pallida var. purpurea are equally sensitive to the clastogenic effects of X-rays

The Tradescantia micronucleus test is a sensitive bioassay for mutagenesis that may be employed both under field and laboratory conditions. This test has been standardized mostly on the basis of the results obtained with clone 4430. However, this clone is not well adapted to tropical weather, frequently showing problems with growth and flowering. In addition, it is attacked by parasites and insects, a fact that limits its use in field studies aiming at the biomonitoring of air pollution. In the city of Säo Paulo, Tradescantia pallida (Rose) Hunt. var. purpurea Boom is widely distributed as an ornamental plant in gardens and along roadsides and streets, mostly because of its natural resistance and its easy propagation. In this report, we present dose-response curves indicating that the sensitivity of T. pallida and clone 4430 to X-radiation (1, 10, 25 and 50 cGy) is similar. The results confirm our previous suggestion that T. pallida represents a good alternative for in situ mutagenesis testing in tropical regions, especially biomonitoring studies in which the exposure conditions may not be fully controllable